1. Field of the Invention
The present invention relates generally to power switching circuits having transformer isolation, and more specifically, to a method and apparatus that provide digital feedback from an analog-to-digital converter (ADC) through a transformer that supplies power and/or clock signals from a winding that is isolated from the ADC circuit.
2. Background of the Invention
Power switching circuits and other circuits that provide for control of and/or measurement of high power/high voltage systems typically require isolation of the high power/high voltage portion of the system from digital control and/or measurement circuits. A transformer is typically used to provide an isolation circuit in such systems. For sensing circuits, the local sensing circuit power supply is typically derived from the high power/high voltage side of the isolation circuit, or provided as a separate power supply. Additionally clock and control signals are generated or provided locally to the sensing circuit, if required. Circuits such as voltage-to-frequency (V/F) converters are frequently used for sensing in such applications, due to their low cost and lack of control/clock signal requirement.
However, in systems having digital control of high power/high voltage circuits, use of an ADC is desirable for sensing, with the consequent cost of additional clock and power supplies provided at the isolated (sensed) side of the transformer.
Therefore, it would be desirable to provide a transformer-isolated ADC circuit that does not require clock or power supply components at the isolated sensing side of the transformer.